In the particular field of electricity installations, experience has shown that earthquakes can cause much damage, particularly to high tension stations where high power circuit-breakers are employed.
Indeed, such devices generally include heavy moving parts disposed at the top of tall insulators, and are consequently highly vulnerable to earthquakes.
More precisely, it has been observed that during major earthquakes, such devices are subject both to horizontal acceleration and to vertical acceleration. While the vertical accelerations present only a minor danger, the horizontal accelerations tend to damage or even destroy such devices.
The applicant has thus sought to develop a protector suitable for protecting such devices from earthquakes.
When observing the response curve of such an installation to a periodic excitation of variable frequency, it will be observed that for equipment built in accordance with standards laying down conditions for the strength of the materials used, that the greatest accelerations appear for frequencies of about 11/2 Hertz, for example, on one particular installation a maximum acceleration of 0.5 g was observed at a frequency of 1.4 Hertz. The acceleration was only 0.2 g at frequencies below 1 Hertz or above 2.8 Hertz.
Taking these observations into account, the protector in accordance with the present invention is interposed between the ground and the apparatus to be protected, and is designed to reduce as much as possible the efficiency with which horizontal stresses are transmitted to the apparatus during an earthquake and to modify the frequency of the oscillation transmitted such that oscillations at the dangerous frequency are attenuated.